<!DOCTYPE html>
<html>
<meta charset="utf-8">
<title>Reference: Active opacity should be rendered if it's inside the display port, even if it's currently offscreen</title>

<style>

#scrollbox {
  border: 1px solid black;
  width: 200px;
  height: 200px;
  overflow: hidden;
}

#scrolledContent {
  height: 1000px;
}

#opacity {
  will-change: opacity;
  opacity: 0.5;
  margin-top: 250px;
  width: 100px;
  height: 100px;
  box-sizing: border-box;
  border: 1px solid blue;
}


</style>

<div id="scrollbox">
  <div id="scrolledContent">
    <div id="opacity"></div>
  </div>
</div>

<script>

document.getElementById("scrollbox").scrollTop = 150;

</script>
